1. Field of the Invention
Embodiments of the present invention relate to a pick-up apparatus and method for reproducing and/or recording data from/to a medium. More particularly, embodiments of the present invention relate to an optical pick-up apparatus and method for recording and reproducing data of various types of optical disks.
2. Description of the Related Art
Recently, various types of optical disks have been widely used for information storage. Accordingly, optical pick-up apparatuses have generally been manufactured to have the capability to record and/or reproduce data to/from more than two types of optical disks. Thus, it has been possible to record/reproduce data on a digital video disk (DVD) type optical disks such as a DVD-R, a DVD-RW, a DVD-RAM, for example, and a compact disk (CD) type optical disks such as a CD-R, a CD-RW and a CD-ROM, for example, by using the optical pick-up apparatus compatible with different optical disk types in a multi-type optical disk compatible optical pick-up apparatus.
However, it is very complicated to manufacture such a multi-type optical disk compatible optical pick-up apparatus because each type of optical disk has its own unique location of pits and/or gap between pits, for example. As a more particular example, the location of pits and the gap in DVD type optical disks may be completely different according to their type, such as DVD-R, DVD-RW, and DVD-RAM types, for example.
FIG. 1 illustrates a comparison between tracks in a DVD-RAM type optical disk and a DVD-R/RW type optical disk.
As shown in FIG. 1, pits can be formed on both a groove area and a land area in the DVD-RAM disk, with the gap between pits being 0.615 μm. Conversely, in the DVD-R/RW disks, the pits can be formed on only the groove area, with the gap between pits being 0.74 μm. Accordingly, a conventional multi-type optical disk compatible optical pick-up apparatus generally includes a hologram enabling the capability to support both the DVD-R/RW and DVD-RAM disks.
FIG. 2 illustrates a conventional multi-type optical disk compatible optical pick-up apparatus.
As shown in FIG. 2, the conventional multi-type optical disk compatible optical pick-up apparatus includes a first optical source 10 to output a light beam of 780 nm wavelength, a second optical source 20 to output a light beam of 650 nm wavelength, a ½ wavelength plate 25 to convert a P polarized light beam output from the first and the second optical sources 10 and 20 into S polarized light beams, a complex prism 30 to change the propagation path of the S polarized light beams from the first optical source 10 and the second optical source 20, a collimating lens 40 to convert the reflected light beam entered from the complex prism 30 to a parallelized light beam, a reflection mirror 45 to reflect the parallelized light beam; a polarized light hologram 50, an objective lens 60, a sensor lens 70 to concentrate the light beam reflected from an optical disk 10a and from the objective lens 60, the polarized light hologram 50, the reflection mirror 45, the collimating lens 40 and the complex prism 30, an optical detector 80 to receive and collect the light beam from the sensor lens 70, and front monitor photo diode 21 and photo diode 11.
For recording and/or reproducing data to/from various types of optical disks having different recording formats, the conventional multi-type optical disk compatible optical pick-up apparatus should include a specially manufactured polarized light hologram for beam dividing. The polarized light hologram 50 is thus specially produced to be operated by a light beam having a predetermined wavelength, e.g., 650 nm, polarized in a predetermined direction, e.g., P-polarized. However, it is very difficult to manufacture the polarized hologram 50 because the weight and size of the polarized hologram are limited. That is, the polarized hologram 50 must usually be manufactured to have less than 0.68 mm of thickness. However, the hologram produced with such a thin thickness may be tilted or bent by heat generated during the operating of the multi-type optical disk compatible optical pick-up apparatus and thus may generate faulty operation of the optical signal detection. Also, there may be an assembling common difference generated between the objective lens 60 and the polarized hologram 50 by including the polarized hologram 50, with the assembling common difference being difficult to eliminate.
As described above, the conventional multi-type optical disk compatible optical pick-up apparatus includes many complicated sub-elements. Therefore, various assembly processes are required to manufacture the conventional multi-type optical disk compatible optical pick-up apparatus, such that the complicated various assembly processes may result in inferior optical disk apparatuses.
In addition, the optical detector 80 generates a focus error (FE) signal and a tracking error (TE) signal for controlling a focus servo and a tracking servo by using a 3-beam method. For example, the FE signal can be generated by an astigmatism method and the TE signal can be generated by using a differential push pull (DPP) method for a DVD±R/RW optical disk type. Conversely, for the DVD-RAM type of optical disk, the optical detector 80 generates the FE signal by using the astigmatism method and the TE signal by using a push pull (PP) method.
However, when the FE signal is generated for focus servo control of DVD-RAM by using anastigmatic of a main light, noise may be generated by the forming of a pre-pit on the land track of the DVD-RAM type of optical disk. The noise causes inaccurate detection of focusing location. Accordingly, performance of the conventional multi-type optical disk compatible optical pick-up apparatus is degraded.